Thermal relay



Nov. 26, 19219. A. J. MOTTLAU 1,736,979

THERMAL RELAY Filed Jan. '14. 1927 2 Sheets-Sheet g WITNESSES: INVENTO 5i. AuqusfJ/Vo /au A? U v :"BY

ATTORNEY peratures of electricall y Patented Nov. 26, 1929 "UNITED STATES inane Parent OFFICE AUGUST J. MOTTLAU, F PITTSBURGH, PENNSlYLVANIA, .[l-FiQIQNQR TO WEQTHtGHU'llSE ELEfLTRIC & MANUFACTURING COMPANY, A @QRPGRATIQN 63F PEL'NSYTAVANM *i'nnnirari Application filed Sannary 1" My invention relates to relays and particularly to thermal relays.

An object of my invention is to provide a thermal relay that may be so adjusted as to be operable to maintain a wide range of average temperatures.

Another object of my invention is to provide a thermostatically actuated simple lever or movement-multiplying mechanism for op aerating an electric switch; and

Another object of my invention is to provide a thermal relay that shall have a switch capable of interrupting or closing an electric circuit instantaneously.

Tn practicing my invention, T provide a switch, a movement-multiplying mechanism for actuating the switch, and a thermo-responsive means for actuating and controlling the movement-multiplying mechanism. The

p switch which T propose to use in the embodiment of my invention is one that is capable of making and breaking electric circuits at a relatively high rate of speed. The switch is of the type that is normally in a circuit 5 closing position. Thus, it will return to the circuit-closing position automatically upon the release of a force that actuates it to a circuit-opening position.

The movement multiplying mechanism comprises a floating lever having a iiulcrum and pivot so located with respect to the ends thereof that a long lever arm and a relatively short force arm are provided. a preferred form of my invention, the lever is supported either by a thermostatically actuated means or by" a thermo-responsive means and the switch.

The distance between the fulcrum and the lever may be varied by adjusting means in accordance with an average condition or temperature to be maintained by the thermal relay. Means are provided also by which the length of the force arm maybe varied in accordance with any temperature differential desired to which the relay is operable.

When controlling temperatures encounteredin refrigerators are to be regulated, ll prefer that the fulcrum be stationary and the pivot movable relativel thereto 3' but if temheated ovens, furthat, Serial Ito. (l mit.

naces, and similar devices are to be regulated, it is preferable that the fulcrum be movable relatively to the pivot.

The movementmultiplying mechanism is applicable to be controlled or actuated by many difierent means, such as thermo-responsrve, pressure responsive, or other similar devices.

The ope ation of the relay is substantially as follows:

Vt lien the thermo-responsive means has attained a predetermined temperature, a pressure is applied to the force arm of the lever, causing it to rock on its fulcrum, thereby actuating the lever arm into on agement with the switch. ll hen the lever lias rocked on its fulcrum through a certain angular space, the switch is actuated to its circuit-opening position. Upon the cooling of the thermoresponsive means, the lever is rocked in the opposite direction on the fulcrum by spring means or by the self-resettingswitch, thereby actuating the switch to its circuit-closing position. ll hen. the thermo-responsive means again attains the above predetermined temperature, the aforesaid operation is repeated.

In the drawings, l is a top plan view, partially in section, of the device embodying my invention.

Fig. 2 is a view, in front elevation, of the device illustrated in Fig. l.

Fig. 3 is a view, in front elevation, of the device illustrated in Fig. 2 part of the cover being removed therefrom.

Fig. 4 is a top plan view of a detail embodied intlie fulcrum end of the lever arm of the device illustrated in Figs. l to 3-, inclusive.

Fig. 5 is an end view of the device illustrated in Fig; 4. 1

Fig. 6 is a view, in side elevation, of fulcrum embodied in the device illustrated in Figs. 1,3, 8 and 9; a

Fig. 7 is a view, in section, taken on line VTTVTT of the device illustrated in Fig. 3.

Fig. 8 is a view, in'sectiomillustrating a modification of coacting parts shown in Figs. 1 and 3; and

Fig. 9 is aview, in section, taken on line of El 8.

In Fig. 1 ol the drawings, a'thermal relay 11 comprises a thermo-responsive means 12, a movement-multiplying mechanism 13 and'a circuit-controlling switch 14.

One form of the thermo-responsive means 12 comprises an. elongated tubular member The tubular member 15 is provided with external screw-threads at one end '21 and internal screw-threads at the other end 22. A plug 23, having screw-threaded engagement with the end 22, is provided with a hole '24 through which the portion 17 of the rod 16 pro ects. The rod 16 is secured to the plug 23 by means of nuts 25.

The tubular member 15 may be of any length, depending upon the required sensitivity ofthe relay to temperature changes. The rod 16 and the push rod 18 maybe of such low-expansion material as invar.

The movement-multiplying mechanism 13 comprises a fulcrum wedge 26, a leverarm shoe 27 and an elongated floating lever 28. The shoe 27 is secured to one end of' the lever 28 by such means as pins 31.

One end of the lever 28 is provided with a projection 'or knob 32 that enga es one of the circuit-controlling switch 4, and

the shoe 27 engages a pivot screw 33.

The pivot screw 33 has screw-threaded engagement with the pivot-supporting member 19. One end of the screw is provided with a circular head having a knife edge 34 thereon that directly engages the shoe 27 The lever -arm shoe 27 is illustrated in detail in Figs. 4 and 5 of the drawings. As here shown, the shoe 27 is, provided with a tapered end portion that extends into a slot in the lever 28 in :which position it'is held by the pins 31. 'The other end of the shoe is slotted longitudinally along opposite edges. 'A portion 35 between the slots. is

bent slightly inon'e direction (see Fig. 5) and edge portions 36 are bent slightly in the opposite direction so that the bottom faces of portions 36 are located substantially in the plane of the top face'of the portion 35.

The fulcrum wedge 26 is illustrated in detail in Fig. 6'andcomprises an elongated portion 37 having holes 38 adjacent to the ends thereof, and a pair of laterally-ex. .tending knife-edges39 The knife-edges 39 are so spaced that they rest upon the bot- ,substantially circular.

tom face of the portions 36 of the shoe 27. It is to be noted that the knife-edges 39 and 34 engage the shoe 27 in substantially the same plane.

The switch 14, the movement-multiplying mechanism 13 and the push rod 18 are enclosed in a casing 41 comprising a base 42 and a cover 43. a I

The base 42 is substantially rectangular in lateral and in longitudinal section, with the exception or an end ortion 44 that is T e top edges of the walls of the base 42 are rabbeted (see Fig. 1) for a purpose to be hereinafter set forth.- A flange 45 extends laterally of the circular end portion 44 and is integral with the base 42. A boss 46 on the flange 45 is provided with a hole 47 through which the push rod 18 may move freely, and internal screw threads by means of which the tubular member 15 may be secured to the base '42.

The base 42 is provided with a rectangular opening 48 "and a circular opening 49 for purposes to be hereinafter set forth.

The cover 43 conforms, in contour, to the base 42 and is provided with complementary rabbeted edges on its walls that coop-r erate to form a-rabbt joint with the base.

A hole 51 is located in a circular end portion 52 of the cover 43, 'complemental to the portion- 44, across which extends a bridging member 53. Tapped holes 54 and 55' (see Fig. 7) are located in-the bridging member 53. Pins 56 project through and beyond the memb r 53 and are so spaced between the holes 54 and .55 that they regis'ter with the holes 38 in the fulcrumfwedge 26 and serve as guides along which the fulcrum may move.

A. fulcrum-adjusting screw. 57 having screw-threaded engagement,with the hole 54,

limits the movement of the fulcrum wedge i 26 along the pins-56. A. knob 58, to which a po1nter.59 is attafihed, is suitably secured to the screw 57 by means of which movement of the wedge 26 may be limited, whereby the relay maybe soadjusted that it. responds to any average condition or temperature desired. The hole 51 in the cover 43 is providedwith a cover 61 that is secured to the bridging member. 53 by means of screws fitting into the holes 55.

An insulating bushing 62 projects through the cover 43 and is suitably secured thereto. A reset and guide member 63 projects through the bushing 62 with which it has screwthreaded engagement, into the casing and through an aperture 64 in the lever 28. member 63 restrains the lever 28 from laterah-and longitudinal movement but permits it to move therealong. The cover 43 is secured to the base 42 by means of bolts that have screw-threaded engagement with lugs 65 and 66 in the base 42 The of making the same.

portion 72 tobe confined in an :1

The base 42 and the cover 43 are provided with semi-circular openings located in the ed non-conducting material, such as bakelite,

although I do not wish to be limited to this particular metal or material or to this method The switch 141 (see Figs. 1 and 3) comprises a resilient metallic frame 68 having a pair of spaced elongated apertures 69 adjacent to the long edges thereof. The middle portion of'the sides of the frame are so formed that a section 71 of substantially W-shape isprov'ded. I

A- ortion 72, between the apertures 69, is bent laterally of the frame 68 at the ends thereof, substantially as indicated by the curved end portions 73, thus causing the y relied position (see Fig. 1). A contact member 7st is secured to the portion 72 by any suitable means.

The frame. 68 is secured toa switch base 7 5, of insulating material, by screws 76 that extend through the portion 71 of W-shape and the base 75. The base is provided with a relatively narrow rectangularportion 77 that fits into the rectangular openingKlS and is secured in this position by means of a contact screw 7 8 that extends through the switch base 75, a washer 79 and a pair of nuts 81. .The contact screw 78 is provided with a suitable head 82 that constitutes a cooperating contact for the Contact 7 The contact screw 78 constitutes one terminal of the switch 14, andone of the screws 76 constitutes its other terminal.

An adjusting screw 83 extends through one end of the frame 68 and the bushing 49, by means of which that end of the frame may be bent downwardly towards the switch base 75 to any desired extent and be fixed in this.

position by means of a lock nut. The other end of the frame 68 normally ngages the knob 32 of the lever 28.

The contacts 74' and 82, as illustrated in Fig. 1 of the drawings, are normally in a circuit-closing position,"but, upon bending that end of the frame 68, Whichengages the knob 32 in a direction towards the switch base 75, the portion 72,0f the frame is caused to pass through a state of unstable equilibrium from which it moves, with a snap action, to disengage the contacts 7 1 and 82.

'When that end of the frame 68 is released,

the portion 72 again passes through the state of unstable equilibrium and engages the contact 74 with the contact 82 as illustrated in Fig; 1.

. l With the relative positions of the pivot screw 33 and the fulcrum wedge 26 as illustrated in Figs. 1 and 3"of the drawings, the thermal relay is adapted for controlling the temperatures usually encountered in refrigerators. As shown in Fig. 1, the relay 11 may be assumed to be secured to a wall of a refrigerator and the tubular member 15 to extend into 1 the refri erator chamber through a hole in the wal. The relay 11 is positively secured to the wall by means of bolts 8d that pass through holes 85 in. the flange 45..

l fhen. the temperature within the refrigerator attains a predetermined low value, the tubular member 15 contracts to cause the rods 16 and 18 to so move the knife edge 34: ofthe pivot screw 33 against the lever shoe 27 that the lever shoe engages the knife edges 39 of the fulcrum wedge 26. Upon further contraction of the tubular member 15, the lever 28 is caused to rock on the knife edges 39 until the knob 32 has so bent the frame 68, as previously set forth, that the contact 7 1 has been disengaged from the contact 82.

it is to, be assumed that, upon the disengagement of the contacts 74 and 82, an electric motor or other electric translating device used to drive an artificial refrigerating mafurther cooling of the chamber in which the tubular member 15 may be located.

As the temperature of the tubular member 15 increases, it expands, thereby moving the push rods 1t; and 18 outwardly; therefore, the lever arm shoe 27 tends tomove away from the fulcrum wedge 26 but, because of the resiliency of the frame 68, the shoe 27is held in rocking engagement with the knife edges 39 until the switch and leverassume the positions substantially as illustrated in 1, in which position the contact 74 engages contact 82. The energizing circuit of an electric motor or other device controlled by the switch 1 1 being thus reestablished, the refrigerating apparatus is again set into operatlon.

l/Vhile the average temperature or condition to be controlled is determined by the relative position of the fulcrum wedge 26 with respect to the lever arm shoe 27, the maximum and minimum values of the temperature or condition are regulated by means of the pivot screw 33, as such values are necessarily a function of the length of the force arm, or the distance between the knife edges 3 1 and 39.,

lf the force arm is relatively long, the difference between the maximum and minimum conditions, with respect to' an average condition, will be proportional to its length. The difierence between the maiiimum and minimum conditions is termed a differential, and when specifically relating to temperatures, the difit'erence is known as a temperature 50 F. is to be maintained, the fulcrum wedge 26 may, by way of illustration, be assumed to be in the position substantially as illus trated in Fig. 1. If, however, the avera e temperature to be maintained is 40 F., t e knob 58 is turned in a counter clockwise direction, as indicated in Fig. 2, until the pointer 59 coincides with the 40 mark on the cover 61. Upon a suificient cooling of the tubular member 15, the lever shoe 27 is moved into engagement with the knife edges 39,

V which movement continues until the portion 37 of the fulcrum wedge 26 engages the screw 57 A furthercontraction of the tubular member 15 will rock the lever 28 on the'knife edges 39 until the knob 32 so bends the frame 68, that the contacts 7 4 and 82 become'disengaged. I

. t is obvious .thatthe tubular .member 15 must contract or shorten considerably more to actuate the switch 14 in order to maintain a temperature of 40 than a temperature of' 50, because the-movable fulcrum 26 is posi tioned at a relatively greater distance away from thelever shoe 27.

If the relayll is to maintain a temperature higher than 50 F., the knob 58 is turned in 'a clockwise direction, thereby movin the fulcrum wedge 26 towards the knife e ge 34. of the ivot screw 33. w

T e sensitivity of'the relay 11 is greatly affected by the length of. the tubular member 15, for the greater its length, the greater will be'its increase in length-per degree change in tem erature.

' T e arrangementiof the pivot screw- 33, the fulcrum wedge 26, and .the' lever 28, as illustrated in Figs. 1 and 3 is adapted for controlling temperatures encountered in re-. frigerators and the like, but, in order to control temperatures common to electric ovens, furnaces and the like, I prefer that the arrangement shall be according to that shown in Figs. 8 and 9.

In Figs. 8 and 9, thepivot screw 33, being secured to the casing 41, is stationary relatively to the fulcrum wedge 26 ,and the adjusting screw 57 which are carried by a frame 87.

. The frame 87 is suitably attached to a-push rod 88, similar to the rod 18 (see Fig. 1). A pair of guide pins 86, secured to the frame 87, register with the holes 38 in the wedge 26, whereby the wedge may slide therealong.

ifiaaa'z'a I The screw 57, having screw thread engage-- ment with the frame, may be adjusted to limit the movement of the wedge 26 on the pins 86.

-When the tubular member 15 expands, the

push rod 88 is moved outwardly, thus ac tuating the knife edges 39 into engagementwith the lever-shoe 27, thereby causing the lever 28 to ivot on the knife edge '34. It is to be un erstood that push rods 18 and 88 may be actuatedby pressure derived from sources other than thermal means. A suflicient expansion of the tubular member 15 will actuate the switch 14 substantially as previously set forth herein.

By means of the screw 57 and the pivot substantially as hereinbefore set i of the force arm, a contraction equal to the above value may .be obtained by a temperature change of 1 F.

By my invention, I have provided a thermal relay having one-adjustment for regulating its temperature differential, whereby a predetermined average temperature may bemaintained, and another adjustment for causing the relay to be operative to maintain any desired average temperature.

- Various modifications may be' made in the device embodying my invention without departing from the spirit and scope thereof. I desire, therefore, that only such limitations shall be placed thereon as are imposed by thepr'ior art and the appended claims.

I claim as my invention:

1. The combination with a circuit controlling device, a thermo-responsive means having a knife edge at one end thereof, a knifeedge-pivot means, and a lever operatively connecting the circuit-controlling device and the thermo-responsive means and having opposite faces at one end thereof lying in one 3. The combination with a circuit-controlling device, an ex ansion and contraction 1 member havin a kni e ed e at one end thereof, anadjusta le knife-e geivotmeans located relatively close to the st knife edge, and a lever extending between the circuit-' controlling device and the expansion and contraction member, said lever having longitudinally-extending tongues alternately op- 0 positely bent laterally of the lever, whereby. the opposite surfaces of the tongues operatively engagin the respective knife edges lie in substantia y the same plane longitudinally of the lever. 15 In testimony whereoffl have hereunto subscribed my name this 3rd day of January,

AUGUST J. MOTTLAU. 

